1. Field of the Invention
This invention relates to the field of grinding tools, and in particular, to a clean grinding system for use with rotary grinding tools which contains and collects substantially all dust: created during use of rotary grinding tools.
2. Description of Related Art
Rotary grinding creates enormous quantities of dust. The dust is difficult and tedious to clean up, and in some cases depending upon the nature of the material being ground, can be dangerous to people and animals in particular and the environment: in general. Fiberglass and the kind of paint used on the bottoms of boat hulls to inhibit marine growth can be especially pernicious. In fact, grinding the bottoms of boat hulls is forbidden in many places by boat yards and by the Environmental Protection Agency.
The dust also poses problems for the persons operating the grinding tools. Special protective clothing and masks are often necessary and extraordinary measures must be taken to avoid dust contamination of nearby structures. The boatyard is a good example. Typically, even if the work surface of a boat, particularly a large boat, is well shrouded, so much dust is created and dispersed that the boats on either side of the boat being refinished must also be cleaned. It is not unusual for the clean up time to exceed the grinding time. In some cases, the paint or finish being removed can damage the paint of another boat.
Some efforts have been made to incorporate dust collecting systems into grinding tools. U.S. Pat. No. 5,527,207--Azar, et al. is directed to a dust collection shroud for hand held power tools. A shroud formed in part by a flat, substantially rigid disk has an aperture located at its center that allows passage of the hand tool's drive shaft through the disk. The shroud is connected directly to the tool body by screws which appear to be original equipment to the tool. The outer perimeter of the shroud is formed by a downwardly depending brush, whose bristles extend to or slightly beyond the lower surface of the grinding disk. The bristles include a flexible plastic strip embedded therein, which helps contain the dust and vacuum and provides some stiffening support for the bristles. A vacuum hose is attached to the exhaust port in the disk. The particulates that are removed from the work piece are said to be centrifugally flung from the work piece by the rotating abrasive media and impact into the supporting brush interface. The vacuum source which is attached to the exhaust port by means of a hose, is said to cause air to flow through the supporting brush interface, suspending the loose particulate, and pulling the loose particulates out of the dust collection device. This device cannot be used on contoured work surfaces without losing dust containment. There is no apparent provision for adjusting the vacuum.
U.S. Pat. No. 4,765,099--Tanner also teaches a sanding and dust collecting apparatus. The apparatus comprises an impeller blade assembly, a spindle member, and sanding disc assembly. The housing assembly also includes an upper plate member, an impeller blade housing portion, and a brush housing portion. This structure requires the equivalent of redesigning the basic grinding tool, and in no way represents an accessory which can be used with a variety of grinding tools. The housing appears substantially rigid, and it is expected that operation on a contoured surface would raise the brush at some point, losing dust containment. There is also no apparent provision for adjusting the vacuum.
Brushes are also used for dust containment in U.S. Pat. No. 5,609,516--Courson, et al. and U.S. Pat. No. 5,279,076--Healy, et al. Insofar as brushes may be useful in dust containment, the various references fail to suggest a consensus as to an ideal configuration for such brushes. A first example is the contrary teachings of using and not using a reinforcing shield. A second example is the length of the bristles. Longer bristles might help with contour grinding, but the ends of long bristles are certain to be pulled inwardly and ground up along with the work surface, after which there will be no long bristles.
The prior art dust containment systems fail to address and solve a number of problems. A first problem is the ability to maintain dust containment when grinding a contoured or curved surface. A second problem is establishing an advantageous configuration for the brush forming the outer perimeter of the dust containment device. A third problem is the need to adjust the vacuum to compensate for different kinds of vacuum systems, different brands of rotary grinding tools and the differing nature and size of the dust particulates created by grinding different kinds of materials with different grades of grit.